1. Field of the Invention
The present invention pertains to an air filter unit having a housing which is constructed to provide for insertion of and removal of a barrier or impingement air filter element from a top side of the housing and including a plurality of reverse flow air cleaning nozzles which are mounted on a manifold surrounding an opening in the housing through which the filter element may be inserted and removed without removal of the manifold or nozzle structure.
2. Description of the Prior Art
The continued emphasis on reducing atmospheric pollution caused by air-borne particulate material has placed further demands on the development of suitable impingement or barrier type air filter apparatus by way of reducing the physical size of the apparatus while maintaining a suitable material separation or cleaning function and without unduly stressing or shortening the life of the filter element structure.
In an effort to reduce the overall physical size of air filter apparatus for relatively large scale industrial applications of various types the multiple, cloth bag type filter units have, to some extent, been obsoleted by the development of filter units utilizing so-called pleated paper barrier or impingement type filters. This type of filter element has been used in relatively light duty applications such as filtering combustion air in internal combustion engines of various types where physical size of the filter is of some concern but particulate material loadings on the filter element are usually relatively light.
The adaptation of pleated paper or similar types of porous media filter elements to industrial type filter apparatus has been accomplished in one sense by the so-called derating of the filter element so that it can accommodate relatively high material loading rates and be adequately cleaned as well as withstand repeated reverse air jet type cleaning processes. Such an approach to the improvement of air filter apparatus is described in U.S. Pat. No. 4,218,227 to Robert E. Frey. One reason for the development of the derated pleated paper filter is to minimize pressure losses of the air flowing across the filter element so that the pleated paper filter is competitive with the so called cloth bag type filters.
Prior to the development of the invention in U.S. Pat. No. 4,544,389, the arrangement of mounting cylindrical pleated paper and similar barrier type filter elements within a filter housing was necessarily complicated by the structure of the air pressure pulse or shock wave type reverse air jet cleaning devices. This prior art type structure required that the filter element be removed from the sidewall or bottom wall of the filter housing and which thereby required entry into the filter housing from the so called "dirty" side of the filter unit. This type of arrangement is unattractive for several reasons including the disadvantage that service personnel are unavoidably contaminated with the particulate material being removed from the filter during servicing and handling of the filter element, the handling of the filter element is difficult, insertion of and removal of the filter element with respect to the housing is a cumbersome and difficult process and the physical size and construction of the filter housing is complicated. It is desirable in most filter applications that the filter element be removable from the top of its housing which advantageously can provide for access to the "clean" air side of the housing. This simplifies filter unit construction and does not require that service personnel become unduly contaminated by the material being separated from the air flow stream being filtered.